Research undertaken by 3M in St. Paul, Minn., culminated in the demonstration of the world's first laser diodes fabricated from II-VI semiconductor materials. These devices emit coherent radiation at 490 nm in the blue-green portion of the spectrum. They are disclosed generally in the Qiu et al. U.S. Pat. application Ser. No. 07/700,580, filed May 15, 1991 and entitled Method For Making An Ohmic Contact For P-Type Group II-VI Compound Semiconductors, and the Haase et al. article Short Wavelength II-VI Laser Diodes, Conference Proceedings for Gallium Arsenide and Related Compounds, 1991 Institute of Physics Conference Series, No. 120, pp 9-16.
There remains a continuing need for improved II-VI laser diode technology. For widespread commercial viability, the laser diodes must be relatively simple in construction and inexpensive to manufacture. The devices must also be capable of operation at relatively low voltages.